Disazo pigments having improved heat resistance using lower alkyl and phenyl esters of acetoacetanilide

Abstract

A disazo pigment is prepared by coupling the tetrazo compound of 3,3'-dichlorobenzidine with an acetoacetanilide compound which is other than those represented by the below-described general formula (I) and is free of water-soluble groups. In the present invention, about 0.5-50 mole % of the acetoacetanilide compound is replaced by a compound represented by the following general formula (I): ##STR1## wherein R means a methyl, ethyl, propyl or butyl group or a substituted or unsubstituted phenyl group.

We claim: 
     
       1. A disazo pigment which is produced by coupling a tetrazo compound of 3,3'-dichlorobenzidine with (a) an acetoacetanilide compound other than those represented by the formula I, said acetoacetanilide compound being free of any water-soluble groups, and (b) about 0.5-50 mole % of an acetoacetanilide compound, based on the total amount of the acetoacetanilide compounds, having the formula I: ##STR3## wherein R is a C 1  -C 4  alkyl, phenyl or phenyl which is substituted by methyl, ethyl nitro or chloro. 
     
     
       2. The disazo pigment as claimed in claim 1, wherein the acetoacetanilide compound being free of any water-soluble groups is selected from the group consisting of acetoacetanilide, o-chloroacetoacetanilide, p-chloroacetoacetanilide, 4-chloro-2,5-dimethoxyacetoacetanilide, 2,4- dimethoxyacetoacetanilide, o-acetoacetanisidide, o-acetoacetotoluidide, 2,4-acetoacetoxylidide, p-acetoacetanisidide, p-acetoacetotoludide, 4-chloro-2-methyl-acetoacetanilide, p-ethoxyacetoacetanilide, 4nitro-2-methylacetoacetanilide, 4- acetoacetaminiphtalimide, 5-acetoacetaminobenzimidazolone, 4-benzoylamino-2,5-diethoxyacetoacetanilide and 4-acetylaminoacetoacetanilide. 
     
     
       3. The disazo pigment as claimed in claim 2, wherein the acetoacetanilide compound is o-acetoacetotoluidide or p-acetoacetotoluidide. 
     
     
       4. The disazo pigment as claimed in claim 1, wherein the COOR group is para to the CH 3  COCH 2  CONH group in the general formula (I). 
     
     
       5. The disazo pigment as claimed in claim 1, wherein R is an ethyl or butyl group in the formula (I). 
     
     
       6. The disazo pigment as claimed in claim 1, wherein the compound represented by the formula (I) is p-carboxyethyl acetoacetoanilide or p-carboxybutyl acetoacetoanilide. 
     
     
       7. The disazo pigment as claimed in claim 1, wherein 1-50 mole % of the acetoacetanilide compound is replaced by the compound represented by the formula (I). 
     
     
       8. The disazo pigment as claimed in claim 7, wherein 3-23 mole % of the acetoacetanilide compound is replaced by the compound represented by the formula (I). 
     
     
       9. The disazo pigment as claimed in claim 1, wherein 3,3'-dichlorobenzidine is converted to its tetrazo compound with an inorganic acid and a nitrite at a low temperature in water. 
     
     
       10. The disazo pigment as claimed in claim 9, wherein the inorganic acid and nitrite are hydrochloric acid and sodium nitrite respectively and the conversion has been effected at 5°-0° C. in the presence of ice. 
     
     
       11. The disazo pigment as claimed in claim 1, wherein prior to the coupling of the tetrazo compound, the compound of the formula (I) and the acetoacetanilide compound are converted into a coupler solution by dissolving the compound of the formula (I) and the acetoacetanilide compound in water with an alkali, followed by neutralization with an organic acid to coprecipitate the compound of the formula (I) together with the acetoacetanilide compound. 
     
     
       12. The disazo pigment as claimed in claim 11, wherein a filtration step is included before the neutralization step so as to remove any insoluble matter. 
     
     
       13. The disazo pigment as claimed in claim 11, wherein the alkali and organic acid are caustic soda and acetic acid respectively. 
     
     
       14. The disazo pigment as claimed in claim 11, wherein the coupling of the tetrazo compound is effected by adding an aqueous solution of the tetrazo compound dropwise to the coupler solution. 
     
     
       15. The disazo pigment as claimed in claim 11, wherein the coupling of the tetrazo compound is effected by adding the coupler solution dropwise to an aqueous solution of the tetrazo compound. 
     
     
       16. The disazo pigment as claimed in claim 1, wherein about 1-10 mole % of the acetoanilide compound which is free of any water-soluble groups is replaced by said acetoacetanilide compound of the formula I.